JPH0116048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of configuring a beam forming circuit called a resistive coupling matrix among beam forming circuits of a multi-beam array antenna.

The resistive coupling matrix consists of a 4-phase phase divider that divides the input signal into four signals that differ in phase by 90 degrees, and a 4-phase phase divider that divides the input signal into four signals that differ in phase by 90 degrees.
This circuit consists of a group of coupling resistors that couple the signal and the output addition line, and by appropriately selecting the resistance values of the two signals and the coupling resistor, it is possible to take out a signal with an arbitrary phase to the output addition line. This beam forming circuit has the excellent feature that it can be applied to an array antenna with any element arrangement and can form multiple beams in any direction. Since it can be constructed relatively easily using the following, it is particularly suitable as a beam forming circuit for a multi-beam antenna mounted on a satellite. However, since this is a lossy circuit, it is usually used in intermediate frequency bands. Examples of beam forming circuits using four-phase phase splitters and coupling resistors have already been developed at Massachusetts Institute of Technology (MIT),
Lincoln Laboratory Technical Report 1960 Part 2, Chapter 4, No. 228 S. Mr. Spoelly (S.
Spoerri)'s paper ``From July 1, 1959 to July 1960
"Fixed beam forming in phased array radar research"
in“Phased Array Radar Studies,
1July1959to1July1960,”) and ESA Journal (European Space Agency Journal)
1980Vol.4, pp.319-336, R. Mr. Coirault and D. Coirault. W. Kriedte's paper “L-band multi-beam formation: method using phased array”
(Multibeam Generation at L-Band:A
Phased-Array Approach).

By the way, the number of connection points in this matrix is 2×, where N is the number of antenna elements and M is the number of beams.
In addition, the number of elements generally increases in proportion to the number of beams, so in a multi-beam antenna with a large number of beams, the matrix size becomes extremely large, which causes structural and electrical problems. This caused various problems in terms of performance. Originally, this beam forming circuit could be applied to multi-beam antennas with any element arrangement or beam arrangement, but in the past, it could also be applied as is when there is symmetry in the element arrangement or beam arrangement, which is important for practical use. Therefore, the practical range was limited due to the problems associated with the increase in size.

The present invention is aimed at significantly downsizing and simplifying the beam forming circuit of a multi-beam array antenna by utilizing symmetry when there is symmetry between the arrangement of element antennas and the beam arrangement. .

FIG. 1 shows an example of the configuration of a known resistance-coupled resistor matrix. Now, to explain the case of the receiving antenna, in the figure, 1-1, 1-2,
..., 1-N are input terminals, and there are N corresponding to the number of antenna elements. 2-1,..., 2-N are four-phase phase dividers, 3R11, 3R12,..., 3RNM are resistors coupled to the 0° or 180° phase line, 3I11, 3I
12,...,3INM are resistors coupled to the phase 90° or 270° line, 4-1, 4-2,...4-M are output addition lines, 5-1, 5-2,...5-M are outputs There are M terminals corresponding to the number of beams in the multi-beam. Here, R and I are subscripts meaning the real part and imaginary part of the signal, respectively. Further, 6 is a terminating resistor for preventing reflection. When used as a transmitting antenna, each input terminal 1-
Signals for forming each beam are input to 1, 1-2, ... 1-N, etc., and each output terminal 5-1, 5-2, ... 5-
Since the basic operation is the same except that M, etc. are connected to each element, the case of the receiving antenna will be explained below. Note that the same reference numerals represent the same or corresponding parts throughout the figures from FIG. 1 to FIG. 5.

The signals received by the N element antennas are frequency-converted to an intermediate frequency while maintaining coherency, and are input to the input terminal 1 of the beam forming circuit shown in FIG.
Input to 1, 1-2, ...1-N. Here, the circuit from the antenna to the high frequency amplifier to the frequency converter is not shown. Each input signal is divided into equal amplitude signals having phases different by 90° by four-phase phase dividers 2-1, . . . 2-N, etc. Out of these, two appropriate signals with a 90° phase difference are connected to coupling resistors 3R11, 3R12,...3 whose resistance values are determined based on the required phase.
When coupled to output summing lines 4-1, 4-2, . . . 4-M via RNM and 3I11, 3I12, . . . 3INM, a signal with an arbitrary phase shift is obtained. When the signals from each antenna element are given a necessary phase shift and their outputs are added, a combined output corresponding to a radiation beam in a specific direction is taken out at one output terminal. Therefore,
By preparing a plurality of output addition lines to construct a matrix circuit as shown in FIG. 1, and appropriately selecting the resistance value of each coupling resistor, a beam forming circuit for a multi-beam array antenna can be constructed.

This beam forming circuit has a simpler and more compact hardware configuration than other types of circuits such as the Butler matrix, but as the number of beams increases, the circuit also becomes larger and the size increases. In addition to mechanical problems such as weight, mechanical resonance, etc., which occur during satellite loading, the following electrical performance problems also occur. In this circuit, the resistance coupling must be sufficiently small so as not to affect the impedance of the input/output lines. Moreover, the larger the number of bonding points, the smaller the individual bonds must be. Therefore, the resistance value of the coupling resistor needs to be sufficiently larger than the line impedance. Usually several 10M
At an intermediate frequency of Hz, the line impedance is a few ohms.
from several 10 Ω to several 100 Ω to several kΩ
A coupling resistance in the range of is used. However, in such a frequency band, the influence of reactance due to the distributed capacitance of the resistor itself cannot be ignored, and this causes an error in the phase shift. Since the influence of reactance is more pronounced as the resistance value increases, the beam forming characteristics deteriorate as the number of beams increases in the beam forming circuit.

Furthermore, as the size of the circuit increases, the length of the output addition line increases, and a problem arises in that the phase change due to the difference in line length from each element cannot be ignored and must be corrected.

All of these problems are caused by the large number of coupling points in the matrix, so if the number of coupling points can be reduced by sharing coupling resistors, most of the above problems can be solved.

By the way, many of the multi-beam array antennas in practical use have symmetry in their element arrangement and beam arrangement, but conventionally, even for such antennas, a circuit with the configuration shown in Figure 1 was used as is. Because it was used, it had the disadvantages mentioned above.

In order to eliminate this drawback, the present invention utilizes the symmetry of a beam forming circuit for a multi-beam array antenna that has symmetry in its element arrangement and beam arrangement to reduce the number of coupling points, thereby reducing the size and weight of the beam. This realizes a beam forming circuit with excellent forming characteristics, and will be explained in detail below with reference to the drawings.

First, the symmetry of the element arrangement and beam arrangement will be explained. FIG. 2 shows a symmetrical ring array and coordinate system. This array is placed on the XY plane so that the center of the ring coincides with the origin O of the coordinate system, and the direction of the observation point P is polar coordinates (θ,
φ). On each ring, all or part of the element antennas form a pair of two elements, and the pairs are arranged at point-symmetrical positions with respect to the center of the ring. In this figure, for example, element 7-n' constitutes a symmetrical pair with respect to element 7-n.
Arrays with such symmetry include commonly used square arrays, triangular arrays, etc.
Includes many planar array antennas.

Next, the symmetry of the beam arrangement will be explained. Regarding beams, all or part of the beams form a symmetrical pair. For example, in Figure 2, if one beam is oriented in the θ and φ directions, the paired beam is oriented in the θ and φ+π directions. suitable for

Now, when examining the excitation phase of a multi-beam array antenna having symmetry in the element arrangement and beam arrangement as described above, it is found that the following relationship exists.

(1) The phases of two elements at symmetrical positions to form any one beam are equal in magnitude and opposite in sign. That is, the excitation signals of the two elements are in a complex conjugate relationship with each other.

(2) When forming two symmetrical beams, the excitation signals for the two beams of an arbitrary element antenna are in a complex conjugate relationship with each other.

Figure 3 is a phase vector diagram, 8a and 8b in the figure.
represents the phase relationship of mutually complex conjugate signals. Corresponding to the beam forming circuit shown in Figure 1, for two complex conjugate signals, the real part component of the phase is 8
It can be seen that c has the same size and sign, and the imaginary components 8d and 8d' have the same size and opposite signs.

By utilizing this property, it is possible to share the four-phase phase divider and the resistance matrix section for two input signals that are complex conjugate to each other, and to obtain two output signals that are complex conjugate to each other, it is possible to combine It becomes possible to share a resistor.

Figure 4 shows an example in which the input circuit is shared, 1-n and 1-n' are terminals of symmetrical elements, and 9a, 9b, 9c are π
- Hybrid, 10 is a π/2 fixed phase shifter. Assuming that the complex conjugate input signals from terminals 1-n and 1-n' are A and B, respectively, the two signals obtained after passing through the π-hybrid 9a are one of the sum signal A+B and the other of the difference signal A. -It becomes B. The sum signal is then converted to another π-hybrid 9b
As its output, two signals with a phase of 0° and 180° are obtained, and one of these signals is connected to a coupling resistor 3 whose resistance value is determined by the required phase.
It is coupled to output addition lines 4-1,...4-m,...4-M via Rn1,...3Rnm,...3RnM.
Therefore, the real parts of the combined output for signals A and B are equal in size and sign.

On the other hand, the difference signal A-B is transmitted through a 90° fixed phase shifter 10.
After receiving a phase deviation of 90° by passing through
is input into the π-hybrid 9c, and as a result,
Phases of 90° and 270° are obtained. Among these, one signal passes through coupling resistors 3In1,...3Inm,...3InM whose resistance value is determined based on the required phase.
It is coupled to output addition lines 4-1,...4-m,...4-M. Therefore, the imaginary parts of the combined output for signals A and B are equal in magnitude and opposite in sign.

As a result, output terminals 5-1,...5-m,...5-
A signal obtained by adding a complex conjugate phase shift to the complex conjugate input signals A and B is extracted from M. Therefore, the coupling resistance 3Rnm etc.
If the resistance value such as Inm is selected appropriately, input terminal 1-n
The signals from 1-n' and 1-n' are added together in phase and obtained at output terminal 5. In the case of the conventional system shown in Fig. 1, separate phase distribution circuits and coupling resistors were required for the two symmetrical inputs, but in the case of the present invention, two symmetrical inputs are required in one system. An output signal for the input will be obtained. Therefore, in the case of an array antenna in which all antenna elements form symmetrical pairs, the number of input circuits is reduced to half that of conventional beamforming circuits.

Next, a configuration of a resistance matrix that uses the complex conjugate nature of the output signal to reduce the number of coupled resistances by half will be described. In the case of a receiving multi-beam antenna, this means that for two symmetrical beams,
This means that the joint resistance is shared.

Figure 5 shows an example of this case, and the input side circuit is the same as the original in Figure 1, but the output addition line is
Through coupling resistors 3R1m,...3RNm, a line 4Rm that is coupled only to the real part (0° or 180°) of the four-phase phase-divided line and coupling resistors 3I1m,...
It is divided into a line 4Im that couples only to the imaginary part (90° or 270°) via 3INm, and each is combined with the signal from each element antenna through a coupling resistance group, and then combined by a π-hybrid 9d. . As a result, the sum and difference of the real part and the imaginary part are output to the two output terminals 5-m and 5-m', respectively. Since these signals are in a complex conjugate relationship with each other, two symmetric beam outputs are obtained at 5-m and 5-m'. Comparing this with the original form shown in Figure 1, it can be seen that the number of output addition lines is the same, but the number of coupling resistors is halved.

As explained above, according to the present invention, by utilizing the symmetry of a resistively coupled beam forming circuit for a multi-beam array antenna that has symmetry in its element arrangement and beam arrangement, which is often used in practical applications, The number of connection points can be significantly reduced. For example, if all element antennas and all beams have symmetry, the number of connection points in the matrix will be 1/4 of the original shape. This has the advantage of making the beam forming circuit smaller, lighter, and easier to manufacture.In addition, electrically, it is possible to use a resistor that is less affected by reactance, resulting in a beam with good beam forming characteristics. Since it also has the advantage that a forming circuit can be obtained, it is particularly effective in realizing a beam forming circuit for a multi-beam array antenna mounted on a satellite with a large number of beams.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a known resistive coupling matrix, Fig. 2 is a diagram showing a planar array antenna consisting of pairs of elements placed symmetrically and a coordinate system, and Fig. 3 is a diagram showing a complex conjugate excitation signal. 4 is a block diagram showing an embodiment of the input side circuit according to the invention as claimed in claim 1, and FIG. 5 is a vector diagram showing the phase relationship of the invention as claimed in claim 2. FIG. 2 is a block diagram showing an example in which the number of coupled resistances is reduced by utilizing the complex conjugate property of . 1-1, 1-2,...1-N...Input terminal, 2-
1,...2-N...4-phase phase divider, 3R11,3
R12,...3RNM and 3I11, 3I12,...
3INM...Coupling resistance, 4-1, 4-2,...4-
M...Output addition line, 5-1, 5-2,...5-M
...Output terminal, 6...Terminal resistor, 7-n and 7-
n'...Symmetric array element pair, 8a and 8b...Antisymmetric phase vector, 8c...Real component of phase vector, 8d and 8d'...Imaginary component of phase vector, 1-n and 1-n' ...Input terminals corresponding to symmetrical elements, 9a to 9d...π-hybrid, 10
...π/2 phase shifter, 4Rm and 4Im...Output addition lines, 5-m and 5-m', which couple only the real part and only the imaginary part of the outputs from the four-phase phase divider, respectively. Output terminal for symmetrical beams.

Claims (1)

[Claims] 1. In a multi-beam forming circuit in which coupling resistors corresponding to each phase are connected in a matrix between a plurality of four-phase phase distributors corresponding to a plurality of inputs and a plurality of output terminals, a mutually complex conjugate relationship is established. A multi-beam forming circuit characterized in that the four-phase phase divider and the number of coupling resistances of the matrix are reduced by sharing the four-phase phase divider and the coupling resistance section for two input signals in the multi-beam forming circuit. 2. In a multi-beam forming circuit in which coupling resistors corresponding to each phase are connected in a matrix between multiple 4-phase phase dividers corresponding to multiple inputs and multiple output terminals, the output summing line is connected to each 4-phase phase divider. It consists of two sets: a resistor and summing line that connects only the real part of the four outputs, and a resistor and summing line that couples only the imaginary part of the four outputs, and by combining the outputs of these two sets using a hybrid, A multi-beam forming circuit characterized in that it obtains two mutually complex conjugate output signals with minimum coupling resistance.